Manufacture of motor fuel



Patented Jan. T8, 193

,iati

- :I E ACTURE 0F MOTOR FUEL Waldo 0. am an Carroll A. Hochwalt, Dayton,

@hio, assignors to Monsanto Chemical Compally, St. Louis, M0,, a corporation of Delaware No Drawing. Application .iune 29, 1938, Serial No. 87,910

6 Claims.

The present invention relates to a process of treating gasoline, motor fuels, and similar distillates to improve their properties, especially in regard to gum formation, sulphur content, and similar characteristics.

The principal object of the invention is to provide a more efficient and economical method of producing gasoline and similar motor fuel distillates.

Heretofore, it has been proposed to remove gum from gasoline by treatment with various reagents. Not infrequently a reagent such as phosphoric acid, zinc chloride solution and the like, will remove the gum from a particular petroleum product but will not remove enough of the sulfur impurities to pass the specifications for motor fuels without ancillary chemical treatment.

Thepresent invention affords an inexpensive and convenient means for accomplishing substantially complete degumming of a gasoline product and sufficient desulfurization to pass the sulfur specification even in the case of the very sour grades of petroleum products.

According to the present invention a gasoline I is treated with a metal'oxide, such as an alkaline ferric oxide, and then subjected to a treatment with phosphoric acid whereby a marked reduction in sulfur content, as well as in gum-forming constituents, is effected, while at the same time the olefinic nature of the fuel is not substantially af fected. The fuel thus treated is remarkably stable with respect to gum and color.

Heretofore the methods of removing gumforming constituents from gasoline and similar I stable with respect to gum and color. The process of this invention obviates such treatments and makes it possible'to effect marked reductions in gum value and sulfur content in a simple and (Cl. ISIS-23) economical manner without producing any substantial reduction in the other desirable properties of the original fuel. The process of the invention usually produces an enchancement of the antiknock value of the fuel instead of the diminution thereof obtained by other refining methods.

According to one method of practicing the invention, the unrefined fuel is passed in vapor form over Alpha-Lux (which is commercially available precipitated ferric hydroxide that is strongly alkaline and used extensively in the industrial and domestic gas industry) at a temperature of 375 to 425 C., at such rate or time of contact, that substantially no cracking results. A suitable rate for a furnace consisting of a heated tube of internal diameter and 5 feet long filled with the ferric oxide in granular formis A gallon of liquid fuel per hour. The vapors are then scrubbed with phosphoric acid maintained at a temperature of about 190 to 200 C., and are subsequently condensed. The optimum temperature for the oxide treatment will vary accord-- ing to the time of contact, the activity and age of the catalyst, the amount and form of the sulfur impurities in the product and the extent of sulfur removal required. A suitable method which we have used to establish the temperature of operation. is to test the final petroleum product to determine the effectiveness of this first step. As the activity of the oxide diminishes the temperature is increased. When effective removal of sulfur is not longer economically possible, the oxide is regenerated in the known manner, preferably with steam, or steam and air. To remove dissolved hydrogen sulfide and the like, the condensate may be washed with a mild aqueous alkali or caustic alkali.

By such a treatment a, gasoline has been improved as shown in the following table. In column I are shown the properties of the original fuel; column II shows the change produced when the vapors are not subjected to the subsequent phosphoric acid treatment, that is, when the vapors are passed only through the ferric oxide; column III represents the improvement obtained by the process as described; column IV shows the improvement obtained by treatment with phosphoric acid alone. The properties weredetermined by the customary methods and were determined by exactly the same procedure for each sample.

III IV Ferric oxide treated Phosphoric acid treatment Origiprocess Gum value (copper dish method, milligrams) 456 Gum test (oxygen bomb stability, minutes) 30 70 Total sulfur content (lamp method,

Mercaptan sulfur content Unsaturation (bromidebromate, centigrams) 54 52 49 50 Absent I 11 IV Positive Negative Poor Excellent Excellent Octane rating (antiknock) 60 60 G3 63 Similar advantageous results have been obtained with a Wide variety of gasolines of differing properties. The method is particularly valuable for fuels with high sulfur contents and high gum values.

The treatment with phosphoric acid may be carried out in the vapor phase as described hereinabove or as further described in the application of Carroll A. Hochwalt and Waldo C. Ault, Serial Number 66,896, filed on March 3, 1936. Alternative procedures consist in effecting the treatment with'the aid of steam, or conducting the treatment in the liquid phase, as described in the applications of Carroll A. Hochwalt and Waldo C. Ault, Serial Numbers 66,893 and 66,895, filed on March 3, 1936. The phosphoric acid may be dispersed on pumice, clay or similar solid material to increase its surface of contact with the material undergoing treatment. For some purposes a treatment with the phosphates of copper, nickel, cadmium, zinc, cobalt, chromium, iron and other metals, according to the method described in the application of Carroll A. Hochwalt and Waldo C.

Ault, Serial Number- 66,894, filed March 3, 1936,

is preferred. When such solid agents are used the treatment can be conducted in two separate units, such as a tube containing ferric oxide and another tube containing the metallic phosphate. or the two catalysts may be placed in the same tube, or the two solid treating agents may be intermingled and used in a single unit.

A concentration of phosphoric acid especially appropriate for the practice of the invention is one which corresponds to tetrapyrophosphoric acid (H6P4013), which has a phosphorus pentoxide (P205) content of approximately 84%. This acid can be made by adding to phosphoric acid, for example, commercial syrupy acid having a phosphorus pentoxide content of about 55%, an additional amount of phosphorus pentoxide until an acid of the appropriate concentration is obtained. Phosphoric acids containing additions of phosphorus pentoxide such that their contents of phosphorus pentoxide range from about 50 per cent and upward, produce satisfactory results in refining most gasolines, but the optimum concentration of the acid and conditions for its usefor any particular purpose are easily determined by previous tests. In the phosphoric acid, a darkcolored liquid will be seen to deposit during the process of treating crude gasolines. This liquid aroaaea has a higher boiling point than the original gasoline passed through the acid and on distillation it yields a clear light colored liquid with a blue fluorescence which is believed to consist of poly-' mers of some of the original gasoline constituents. It is desirable to control the temperature of the phosphoric acid chambers so that little ornone of these polymers are volatilized with the vapors.

To prevent any spray of phosphoric acid or polymer during the treatment, the apparatus is provided with suitable bafiles or towers packed with any non-reactive filling material such as glass,-

coal, coke, etc. These provisions are more fully described in the applications of Carroll A. I-Ioch- Walt and Waldo C. Ault, to which reference has already been made.

The improved process of using ferric oxide with a phosphoric acid treatment produces a result heretofore unexpected of a combination of the two processes. The treatment with the ferric oxide, in some manner which is not clearly understood at present, besides removing a definite proportion of the sulfur bodies present in the original distillate, leaves the unremoved residual sulfur bodies in what might be called an activated condition, that is, in such a condition that they are more completely removed in the subsequent phosphoric acid treatment. It has been found that less advantageous results are obtained if the phosphoric acid treatment precedes the desulfurization treatment and that when two gasolines, (1) an unrefined gasoline, and (2) a gasoline pretreated with ferric oxide, both with an equivalesnt total sulfur content and corresponding in other properties, are treated with phosphoric acid in exactly the same way as described herein, that gasoline previously treated with ferric oxide will have a lower residual sulfur content than the gasoline not previously treated. The action of the ferric oxide appears to affect favorably the susceptibility of the sulfurto removal by treat- 'ment with phosphoric acid or similar gum removing reagent. While the treatment with phosphoric acid to remove the gum is preferred and possesses distinct advantages, other known means for accomplishing this step by polymerization may be employed. For example, acid reacting salts and aqueous solutions thereof have been proposed for this step, such as zinc chloride and the like.

The function of the ferric oxide from ,the above considerations is primarily that of rendering the sulfur compounds in the original gasoline more completely susceptible to removal. Other materials which are effective, especially when rendered distinctly alkaline or basic, are: iron ores, copper oxide, bauxite, aluminum oxide, lead oxide and calcium oxide; in general, alkaline metallic oxides or hydroxides may be used. Salts or metals which can give rise to metallic oxides during the treatment may be employed by placing them in the tube or other suitable apparatus and treating them in such a manner that the oxide remains; thus, for example, the tuoe maybe filled with iron filings and air passed therethrough at a raised temperature until oxidation to ferric oxide hasbeen accomplished. During the treatment some metal sulfides may be formed. Oxidation with air at a raised temperature,-preferably with the addition of steam, is sufficient to reconvert these sulfides to oxides. The oxide, especially when strongly alkaline, activates the sulfur compounds in the original distillate to a form whereby they are more easily removed in the subsequent step and need not of itself have any desulfurizing action.

Inasmuch as the conditions and reagents specified above comprise preferred embodiments of the invention, it is to be understood that the invention is not limited thereto, nor to any theory of the chemical actions herein involved, but is sub- .iect only to the limitations defined in the appended claims.

What we claim is:

1. In the treatment of a cracked distillate of motor fuel boiling range, rich in sulfur and gum forming constituents, to form a distillate of motor fuel quality, the steps which include subjecting the distillate while in vapor phase to a metal oxide which has been rendered distinctly alkaline, 15

whereby sulfur impurities are rendered removable by phosphoric acid treatment and subsequently scrubbing the distillate with phosphoric acid under conditions whereby polymerizable and sulfur containing impurities are removed without substantially reducing the octane number of the motor fuel.

2. In the treatment of a cracked distillate of motor fuel boiling range, rich in sulfur and gum forming constituents, to form a distillate of motor fuel quality, the steps which include subjecting the distillate while in vapor phase to an alkaline ferric oxide, whereby .sulfur impurities are rendered removable by phosphoric acid treatment and subsequently scrubbing the distillate with phosphoric acid under conditions whereby polymerizable and sulfur containing impurities are removed without substantially reducing the octane number of the motor fuel.

3. In the treatment of a cracked distillate of motor fuel boiling range, rich in surfur and gum forming constituents, to form a distillate of motor fuel quality, the steps which include subjecting the distillate while in vapor phase to a distinctly alkaline ferric oxide, whereby sulfur impurities are rendered removable by phosphoric acid treatment and subsequently scrubbing the distillate with phosphoric acid under conditions whereby polymerizable and surfur containing impurities are removed without substantially reducing the octane number of the motor fuel.

4. In the treatment of a cracked distillate of motor fuel boiling range, rich in sulfur and gum forming constituents, to form a distillate of motor fuel quality, the steps which include subjecting the distillate while in vapor phase to a distinctly alkaline ferric oxide, whereby sulfur impurities are rendered removable by phosphoric acid treatment and subsequently scrubbing the distillate with a polymerizing agent under conditions whereby polymerizable gum forming and sulfur containing impurities are rendered removable without substantially reducing the octane number of the motor fuel.

5. The method as defined in claim 4 and further characterized in that the ferric oxide treatment is effected at approximately 375-425 C. and the phosphoric acid treatment is effected at approximately -200 C.

6. The method as defined in claim 4 and characterized in that the ferric oxide is substituted by an alkaline oxide of another metal which has been rendered distinctly alkaline.

WALDO o. AUL'II. CARROLL A. HOCI-IWALT. 

